SIEVEWELL™ is high density cell arraying device which has membrane with nanowells for single cell trapping. SIEVEWELL™ is designed to trap cells at a high single cell rate. Two pores are positioned on the bottom of the nanowell. The pore size of the SIEVEWELL™ is smaller than typical mammalian cells. Thanks to this design, cell loss can be minimized during on-chip staining. This is ideal tool for on-chip rare cell staining and detection like CTCs.